Backing a knit blanket

Hi everyone!

I finished a stockinette baby blanket last week that has a seed stitch border and colourwork letters in two corners. It was my first real colourwork project, and I didn't do it very well, so I went back and fixed it after I figured out where I went wrong. As a result, I have a lot of knots on the back of the work. Since this is a baby blanket, I'd really rather not have that sort of thing where it could be gotten at by little toes or fingers.

I want to back it, maybe with some cotton flannel, but I'm not totally sure what the best way to do that would be. The yarn is 100% acrylic, Bernat's Baby Coordinates, if that matters a lot.

Recipient lives in Canada, as do I, so a blanket with an extra layer just in time for winter isn't going to be a problem. I just want to avoid doing the "lining" wrong.

Should I quilt it somehow? Should I cover the entire blanket, including the border, or just the inside part? Should I sew it with a machine (I have a 1960s Singer) or by hand (I can do either)?

Trust me to take something relatively simple and make it complicated as heck... :P